A virtualization technique is used to operate one or more virtual computers on one physical computer. The virtual computer is referred to as a virtual machine.
An expression of “a computer hosts a virtual machine” means that the computer operates a virtual machine. Similarly to the physical computer, an operating system (OS) and applications are operated on the virtual machine.
The virtualization technique has various advantages. For example, the virtualization technique can improve the operation efficiency of the data center. For example, when each of a plurality of physical servers with a low load is replaced with the virtual machine, it is possible to host a plurality of target functions using one physical server. As a result, the use efficiency of the server is improved.
In recent years, a technique which transfers the virtual machine hosted by a computer to another computer through a network, without stopping the services provided by the virtual machine, has been put to practical use. This technique is referred to as live (dynamic) migration.
The use of the live migration makes it possible to change the arrangement of the virtual machines depending on the situation. For example, when some virtual machines are transferred from a high-load server to a low-load server, the speed and reliability of the service are improved and it is possible to raise service quality. In addition, for example, when all of the virtual machines are transferred from the low-load server and the server is turned off, it is possible to reduce power consumption. For example, when the virtual machine is evacuated from the server in which a failure is more likely to occur, it is possible to enhance the reliability of a process.
For this type of technique, Patent Document 1 describes a technique which transfers the virtual machine hosted by a low-load server to another server and turns off a server which does not host the virtual machine, thereby reducing power consumption.
Non-patent Document 1 discloses an iterative pre-copy system (IPC system), which is one of the live migration systems. In the IPC system, before a computer, which is a transfer destination, takes over the process of the virtual machine, all data required for the virtual machine is transmitted from a computer, which is a transfer source, to the computer, which is a transfer destination. After the computer, which is a transfer destination, takes over the process, no data is transmitted from the computer, which is a transfer source.